插入排序

int insertion_sort(int a[])
{
  int j, t;
  for (int i=2; i<=N; ++i)
  {
    j = i;
    while (j > 1 && a[j] < a[j - 1])
    {
        t = a[j];
        a[j] = a[j-1];
        a[j-1] = t;
        j = j-1; 
    }
  }
}